Fuel cell battery containing flat carbon electrodes



June 1965 K. KORDESCH ETAL 3,

FUEL CELL BATTERY CONTAINING FLAT CARBON ELECTRODES Original Filed Jan.22, 1959 4 Sheets-Sheet 1 INVENTORS KARL KORDESCH /9 SAMUEL H.RAUB

LAWRENCE J .ULINE June 1955 K. KORDESCH E'TAL 3,188,2

FUEL CELL BATTERY CONTAINING FLAT CARBON ELECTRODES INVENTORS KARLKORDESCH SAMUEL H. RAUB LAWRENCE J.UL|NE 4 Sheets-Sheet 3 June 8, 1965KORDESCH ETAL FUEL CELL BATTERY CONTAINING FLAT CARBON ELECTRODESOriginal Filed Jan. 22, 1959 .Illl'lll llllllllllllllllllllll 1INVENTORS KARL KORDESCH SAMUEL H.RAUB LAWRENCE J.ULINE B) ,Q Q

ATTOR r June 8, 1965 K. KORDESCH ETAL 3,

FUEL CELL BATTERY CONTAINING FLAT CARBON ELECTRODES Original Filed Jan.22, 1959' 4 Sheets-Sheet 4 INVENTORS KARL KORDESCH SAMUEL H.RAUBLAWRENCE J.ULINE Br H (2 W ATTORN V United States Patent 3,188,242 FUELCELL BATTERY CUNTAKNEJG CAFBQN ELECTRGDE Karl Kordesch, Lakewood, SamuelH. 5. Earth, Bay Village, and Lawrence 13. Uliue, Lakewood, Gide,assignors to Union Qarbide Corporation, a corporation of New YorkOriginal application .ian. 22, 1959, Ser. No. 788,39ti. Divided and thisapplication July 13, 1962, Ser. No.

3 Claims. (Ci. 13686) This is a division of application Serial No.788,390, filed January 22, 1959, now abandoned.

This invention relates to fiat electrodes for fuel cells designed tooperate at low voltage and high current.

The fuel cells for which the present electrodes are intended can be ofseveral types. They may, for example, operate by the diffusion ofhydrogen gas through a negative electrode to liberate electrons byionization through an electro-chemical reaction with alkalineelectrolyte.

electrodes. Fuel cells using other fuel gases may also advantageouslyemploy the principles of the instant inven-tion.

The main object of the invention is to provide a rugged, flat, stackedfuel cell battery designed to operate ciliciently at low voltage andhigh current.

Another object of the invention is to provide rugged, flat negative andpositive electrode elements characterized by a low internal resistance.

Another object of the invention is to provide rugged bipolar fuel cellelectrodes having a large effective surface area.

A further object is to provide rugged unit cell electrodes having alarge effective surface area.

In the drawings:

FIG. 1 is a front elevational view partially in section of a fuel cellbattery containing the electrodes of the invention;

FIG. 2 is a plan view of a bipolar half cellular arrangement for thefuel cell battery shown on FIG. 1;

FIG. 3 is a cross-sectional view of a bipolar electrode unit as shown inFIG. 2, and taken along lines 3-3 thereof;

FIG. 4 is a plan view of a complete unit cell of FIG. 1;

FIG. 5 is a cross-sectional view of the unit cell of FIG. I

4 taken along lines 5''5 thereof;

FIG. 6 is a cross-sectional view of a battery assembly containing theelectrodes of the invention;

FIG. 7 is a perspective view showing the enclosure 0 the assembly ofFIG. 6;

FIG. 8 is a lengthwise cross-sectional view of the assembly of FIG. 6; i

FIGS. 9, l0 and 11 are perspective views of electrode "ice bon platesthus made have a porosity of the order of 18 to percent as measured bywater saturation methods. Porosity of the plates preferably is increasedto about percent by heating the plates at 850 to 950 C. in a carbondioxide atmosphere for several hours.

To activate the carbon plates prepared as above outlined, a catalystsolution such as an 0.1 M solution of cobaltous nitrate Oo(NO -6H O andaluminum nitrate Al(NO -9H O, is applied to the plates and heatdecomposed therein to form cobaltic oxide-aluminum complex (CoO'Al O onthe carbon surfaces. This treatment is necessary only for the oxygenelectrodes. To simplify manufacturing operations, however, it is morepractical to treat both the oxygen and hydrogen electrodes in thismanner. The final porosity of the electrodes thus treated ranges from topercent. Following the previously outlined treatments, the hydrogenelectrodes are coated with a suitable hydrogen ionization catalyst suchas platinum or rhodium. Suitably, this can be done by means of a 10percent aqueous solution of chloroplatinic acid or of rhodiumtrichloride, which is painted on the electrode surface, and is thermallydecomposed in a hydrogen atmosphere at a temperature approaching 400 C.to leave only the metal on the hydrogen electrode surface. The range ofA to 8 milligrams of metal per centimeter square gives satisfactoryresults. Good performance is achieved at the two milligram per squarecentimeter concentration of metal on the electrode surface. In additionto platinum and rhodium, it should be noted that other transition metalsfrom Group VIII, including palladium, iridium, ruthenium and osmium ormixtures thereof can be employed to promote rapid hydrogen ionization incells designed to operate at room temperature. Iron and nickel can alsobe used as catalysts to promote hydrogen ionization, but these performbest when the fuel cell battery operates only at high temperatures.

It should be noted that more efiicient electrode operation and longerelectrode life, especially in the case of the hydrogen electrode, can beachieved by coating the electrode surface with a porous sodiumcarboxymethyl cellulose film.

Referring now to the drawing, there is shown in FIG. 1 a frontelevational view of a fuel cell battery generally designated byreference character 10, and comprising a plurality of stacked cellunits, each designated generally by reference character 11, and havingterminal plates 13 and 15. FIGS. 2 and 4 show plan views, respectively,of alternative bipolar half cell and complete cell modifications of theunits shown in FIG. 1. Referring to the bipolar half cell unitmodification of FIGS. 2 and 3, these units have half cell frames 12,which are molded from plastic. Each half cell unit has four tie boltholes 14 at each corner thereof. To avoid shorting, these holes shouldbe insulated from the cell. 'The half cell units are each provided alsowith hydrogen inlet 16, oxygen inlet 17, oxygen outlet 18 and hydrogenoutlet 19, as well as with two other openings 21, which form anelectrolyte well when several half-cell units are superimposed. As shownin cross-section 3-3 of FIG. 3, the half cell frames have two shoulders20 on which rest carbon anode 24 and carbon cathode 26, respectively.\Passing through the plastic frame 12 is an electrolyte inlet 27communicating with electrolyte space 29, which lies intermediate theanode of one unit and the cathode of the adjacent half-cell unit. Eachhalf cell electrode is separated from the other by means of animpervious metal gas a.) the superimposition of the various gas inletsand of the openings designated at 21, provides considerable free spacewithin the battery for electrolyte and gas, and permits hydrogen gas tohave access through hydrogen inlet 16 to anode 24 and hydrogen outlet19, similarly permitting oxygen gas to have access through inlet 17 tocathode 26 and oxygen outlet 18.

While in the above description the cell units have been shown to berectangular, the present invention is naturally not limited to suchconfiguration. Thus there appears in FIGS. 6, 7 and 8 a tubular plasticenclosure 35 into which are inserted carbon electrodes 32 separated by ahollow square plastic separator 34 having slightly smaller dimensionsthan the electrodes. The volume bounded by the spacer, and labeled 33 inFIG. 8, serves as an electrolyte compartment which can be filled bymeans of tube 35 (shown on FIGS, 6 and 7), which passes through a cornerof spacer 34. Water can be added through this tube to maintain constantthe concentration of the electrolyte, since the moisture produced byelectrode reactions and from the evaporation of the electrolyte tends tobe removed by the hydrogen and oxygen streams. The diametricallyopposite spaces labeled 36 and 33 in FIG. 6 are oxygen compartments,while similar spaces 40 and 41 are hydrogen compartments. Entrance tothe oxygen compartment as is provided through inlet tube 42, and oxygenleaves compartment 33 through outlet tube 44; similarly hydrogen inlettube 43 communicates with hydrogen compartment 40, and hydrogen outlettube 46 communicates with hydrogen compartment 40. As shown, the end oftubular enclosure 30 is sealed by means of a circular plastic cap 47. Acopper wire 43 extends through cap 47, and contacts collector dpositioned between the top oxygen electrode and the plastic cap 47,

and may be suitably connected to battery terminals shown as 13 and inFIG. 1. Suitably, collector 50 may consist of a thin sheet of silverfoil or of a thin layer of sprayed silver.

FIG. 8 shows a lengthwise cross-section of the cell described above. Thearrows indicate the direction of oxygen gas flow through oxygencompartments 36 and 38 from oxygen inlet tube 42 through oxygen outlettube 44.

A number of fiat electrode structures may be used in accord with thepresent invention. Thus on FIG. 9 there is shown a bipolar electrodehaving a first set of holes 52 drilled on the side of the electrodeserving as the hydrogen electrode, and another set of openings 54 on theother side of the electrode at righ angles thereto, and serving as theoxygen electrode.

A further embodiment of the electrodes of this invention appears on FIG.10. In this embodiment two separate carbon plates 56 and 58 havinglengthwise holes drilled or formed by molding into them are used. Theplates may be cemented together with a thin layer of gasimpervious,conductive cement. In the embodiment shown on FIG. 10, a thin sheet ofconductive material 60, such as silver or titanium or impervious carbonis cemented at 62 between the plates. The arrangement shown prevents anydiffusion of the gases between the two electrodes.

A further modification of the invention is shown on FIG. 11. It consistsof two flat plates 66 and es, having grooves along one face of each.plate. The plates, separated by a thin impervious carbon plate or metalsheet 70 are so placed that the grooved sides face each other. Thegrooves indicated may be formed by machining, extrusion or molding.

Still another embodiment of the invention is shown on FIG. 12. Thisstructure may be termed sandwich in that it consists of twosmooth-surfaced porous carbon plates 72 and 74, which are cemented bymeans of a conductive cement to a centrally located impervious carbon orgraphite plate '76. Plate '75 is corrugated on both faces. The grooveson one face may run parallel or at an angle to those on the oppositeface, as shown in the (J. :figure. An advantage lies in using thevertical parallel arrangement of the grooves in that both hydrogen andoxygen gases will thus flow vertically through the assembled battery,thereby eliminating moisture problems encountered when one of the gasescontacts the carbon surface by horizontal flow.

A structure alternate to that shown on FIG. l2 is shown on FIG. 13. Herea corrugated barrier 78, composed of titanium, steel or imperviouscarbon, is substituted for the grooved impervious carbon plate shown onFIG. 12.

Two additional variants of the invention appear in FIGS. 14 and 15. FIG.14 shows a bipolar electrode structure wherein two carbon plates 80, 32,having one corrugated side, are positioned facing each other, but withan impervious metal barrier Q4 placed between them. FIG. 15 shows acomplete unit cell in which carbon anode 83 and cathode are backed bygas-impervious metal barriers and contact plates 86 and 84,respectively. The central space 92 between the carbon electrodes servesas an electrolyte compartment when the unit cell is sccured withinappropriate framework. In one case (FIG. 14) the arrangement constitutesa bipolar electrode which when placed in series with others like it, hasan electrolyte space provided between the bipolar electrodes. In theother instance (FIG. 15), the structure is a unit cell having theelectrolyte space already present.

The efiiciency of a fuel Cell of the type herein described has beencalculated to be far greater than that of conventional tubular electrodearrangement, as the following examples will illustrate: A cell (12inches long by 4 inches diameter) containing nine tubular carbonelectrodes inch OD.) and having conventional metal current collectorsproduced 0.84 volt at 10 amperes. The internal ohmic resistance of thissystem i at least in the order of 0.004 ohm, so that actual terminalvoltage is 0.84 to 0.04:0.80 volt or an output of 8 watts per cell. Theproblem, although not serious up to this point, becomes serious if thecell operates at a current of 50 amperes where the voltage drops to 0.84to 0.20:0.64 volt. This represents a power loss of approximately 25percent.

In a cell of the same volume as above, but containing the disclosed fiatplate structures, the internal resistance of the bipolar electrode iscalculated to be less than 0.001 ohm per cell, which when operated at 10amperes, produces a negligible voltage drop of 0.01 volt. Increasing thecurrent to 50 amperes results in a loss of only 0.05 volt per cell orthe production of 0.79 volt (39.5 watts/ cell) at the terminals. Thepower loss in this instance is only 6 percent instead of 25 percent inthe case of the tubular construction.

The present cell operates with conventional liquid electrolytes, thenature of which depends on the gases supplied thereto. Thus, in a fuelcell producing electricity from hydrogen and oxygen, the electrolytepreferably should be 7 to 15 Normal potassium hydroxide, to which may beadded from 0.01 to 2 percent by weight of potassium osmate. Where thefuel cell is to function with hydrogen and chlorine gases, a preferredelectrolyte is 4 Normal hydrochloric acid.

The structure herein disclosed is designed to operate at a range of gaspressures ranging from about to about 10 atmospheres, at temperaturesranging from about 20 C. to about C.

The fuel cell of this invention is suitable for use in communicationssystem, mobile power units and stand-by power plants.

We claim:

it. A fuel cell battery comprising: (A) a generally tubular enclosure ofa non-conductive material; (B) a plurality of pairs of substantiallyrectangular carbon electrodes, each electrode pair comprising (1) a fuelelectrode having a fuel gas surface, an electrolyte surface and fourouter edge surfaces, (2) an oxidant electrode having an oxidant gassurface, an electrolyte surface and four outer edge surfaces, the gassurface of said fuel electrode facing rier defining a plurality ofsubstantially straight fuel gas channels, the opposite side of saidgas-impervious barrier enclosure and through a corner of each of saidspacer,

and the gas surface of said oxidant electrode defining a plurality ofsubstantially straight oxidant gas channels, said conductivegas-impervious barrier being in conductive contact with both of saidelectrodes; (C) a plurality of non-conductive annular spacer elements ofsubstantially rectangular perimeter separating said plurality ofelectrode pairs, said non-conductive spacer elements being disposedaround the periphery of the electrolyte surfaces of said electrodes, oneof said spacer elements together with the electrolyte surface of theoxidant electrode of one of said electrode pairs and the electrolytesurface of the fuel electrode of the adjacent electrode pair defining anelectrolyte chamber between said adjacent electrode pairs; (E) all fourcorners of each of said electrodes and each of said spacer elementsbeing in gas tight contact with the inner Wall of said tubularenclosure; (F) a first inlet manifold and first outlet manifoldcommunicating with the fuel gas channels of each fuel electrode toprovide circulation of fuel gas across said fuel gas electrode surfaces;(G) a second inlet manifold and second outlet manifold communicatingwith the oxidant gas channels of each oxidant electrode to providecirculation of oxidant gas across said oxidant gas electrode surfaces,said four manifolds being defined by the inner Walls of said tubularenclosure and the outer edge surfaces of said electrodes and said spacerelements; and (H) openings through said tubular elements communicatingwith each of said electrolyte chamber to supply electrolyte thereto.

2. A fuel cell battery as defined in claim 1 wherein each of saidelectrode pairs comprises two porous carbon plates, each plate havinggrooves across one side thereof, the grooved side of each plate beingfastened by means of conductive cement to a conductive, gas-impervioussmooth-surfaced carbon plate disposed between said grooved plates. p 1

3. A fuel cell battery as defined in claim 1 wherein each of saidelectrode pairs comprises two smooth-surfaced porous carbon plates inconductive contact with and separated by a corrugated, conductive,gas-impervious barrier element.

References Cited by the Examiner UNITED STATES PATENTS 2,175,523 10/ 39Greger. 2,276,188 3/42 Greger. 2,901,523 8/59 Justi et al 136-862,969,315 1/61 Bacon 13686 7 3,012,086 12/61 Vahldrick 136-86 JOHN H.MACK, Primary Examiner. JOHN R; srncK, Examiner.

1. A FUEL CELL BATTEY COMPRISING: (A) A GENERALLY TUBULAR ENCLOSURE OF ANON-CONDUCTIVE MATERIAL: (B) A PLURALITY OF PAIRS OF SUBSTANTIALLYRECTANGULAR CARBON ELECTRODES, EACH ELECTRODE PAIR COMPRISING (1) A FUELELECTRODE HAVING A FUEL GAS SURFACE, AN ELECTROLYTE SURFACE AND FOUROUTER EDGE SURFACES, (2) AN OXIDANT ELECTRODE HAVING AN OXIDANT GASSURFACE, AN ELECTROLYTE SURFACE AND FOUR OUTER EDGE SURFACES, THE GASSURFACE OF SAID FUEL ELECTRODE FACING THE GAS SURFACE OF SAID OXIDANTELECTRODE, AND (3) A BARRIER OF CONDUCTIVE GAS-IMPERVIOUS MATERIALBETWEEN THE GAS SURFACES OF SAID PAIR OF ELECTRODES, THE GAS SURFACE OFSAID FUEL ELECTRODE AND ONE SURFACE OF SAID GAS-IMPERVIOUS BARRIERDEFINING A PLURALITY OF SUBSTANTIALLY STRAIGHT FUEL GAS CHANNELS, THEOPPOSITE SIDE OF SAID GAS-IMPERVIOUS BARRIER AND THE GAS SURFACE OF SAIDOXIDANT ELECTRODE DEFINING A PLUARLITY OF SUBSTANTIALLY STRAIGHT OXIDANTGAS CHANNELS, SAID CONDUCTIVE GAS-IMPERVIOUS BARRIER BEING IN CONDUCTIVECONTACT WITH BOTH OF SAID ELECTRODES; (C) A PLURALITY OF NON-CONDUCTIVEANNULAR SPACER ELEMENTS OF SUBSTANTIALLY RECTANGULAR PERIMETERSEPARATING SAID PLURALITY OF ELECTRODE PAIRS, SAID NON-CONDUCTIVE SPACERELEMENTS BEING DISPOSED AROUND THE PERIPHERY OF THE ELECTROLYTE SURFACESOF SAID ELECTRODES, ONE OF SAID SPACER ELEMENTS TOGETHER WITH THEELECTROLYTE SURFACE OF THE OXIDANT ELECTRODE OF ONE OF SAID ELECTRODEPAIRS AND THE ELECTROLYTE SURFACE OF THE FUEL ELECTRODE OF THE ADJACENTELECTRODE PAIR DEFINING AN ELECTROLYTE CHAMBER BETWEEN SAID ADJACENTELECTRODE PAIRS;